Some games played by touch are fine, but for others, you should have a handle. There are a number of gamepads designed for iPads and iPhones that you can use to play with many games on the App Store, Gamevice is generally the most appreciated, along with StellSeries Nimbus and PXN Speedy.
Use the included gamepad to make it easier to control
Perhaps you are using a headset on your PC with speakers on your TV, so why only use the tiny speaker on your iPhone and iPad? A good headset not only helps sound in the game better but also helps detect sound direction (especially useful in FPS shooting game). Open headphones are better for orientation but closed headphones won't bother people around.
Use good headphones for better sound quality
If you're not happy with mobile games and own a PC with an NVIDIA graphics card, you can play PC games right on your iPhone or iPad.
Stream PC game to iOS with Moonlight
Thanks to NVIDIA Gamestream and the free Moonlight app, gamers can stream games directly from PC to iOS and let the computer do the heavy work. Moonlight can also be used with gampad MFI so it looks like you have a small version of NVIDIA SHIELD running on iOS. Once you've played Skyrim on the iPad, you probably won't leave the seat.